Fuel tanks for vehicles include saddle fuel tanks in which the space for storing fuel is divided into a main chamber and an auxiliary chamber.
Known fuel supply devices that use a saddle fuel tank include the fuel supply device disclosed in Japanese Utility Model Application Laying-Open Publication No. 5-77578 (JP-U-05-77578 A). In this fuel supply device, a fuel pump is provided to a main chamber, and the fuel in an auxiliary chamber is directed to the main chamber using a jet pump (transfer means) in order to supply an engine with the fuel stored in the two chambers (main chamber and auxiliary chamber) of a saddle fuel tank.
The abovementioned fuel supply device is configured so that the fuel pump is driven to supply the fuel in the main chamber to the engine, and a portion of the supplied fuel is returned to the main chamber via the jet pump. By returning a portion of the supplied fuel to the main chamber via the jet pump, the inside of the jet pump is negatively pressurized, and the fuel in the auxiliary chamber is directed to the main chamber.
However, since only one fuel pump is provided to the main chamber in the fuel supply device according to JP-U-05-77578 A, the fuel supply device is difficult to adapt to a high-output engine that has a large amount of exhaust.
A fuel supply device provided with two fuel pumps in order to adapt to a high-output engine is disclosed in Japanese Utility Model Application Post-Exam Publication No. 5-45818 (JP-U-05-45818 B).
In the fuel supply device according to JP-U-05-45818 B, two fuel pumps are provided on both sides within the fuel tank, supply pipes are connected to the fuel pumps, and each supply pipe separately extends to the outside of the fuel tank.
Each extended supply pipe is connected to a fuel filter (strainer), and the fuel filters are connected to the engine via the fuel pipes.
According to this fuel supply device, the fuel necessary for a high-output engine can be supplied by simultaneously driving the two fuel pumps.
Among vehicles, a single type of body is sometimes provided with a high-output engine, a fuel-saving engine, or another engine having different specifications.
High-output engines usually have the highest fuel consumption.
Fuel-saving engines also have a low maximum fuel consumption.
The number of fuel pumps provided to the fuel supply device disclosed in JP-U-05-45818 B may be varied in order to adapt to these different specifications of engines.
Specifically, two fuel pumps may be used in specifications provided with a high-output engine, and one fuel pump may be used in specifications provided with a fuel-saving engine.
In a common fuel tank, an open part for accommodating the fuel pump is formed at the top. After the fuel pump is accommodated through the open part, the open part is closed by a cover.
A supply pipe connected to the fuel pump is extended to the outside of the fuel tank via a passage hole in the cover and connected to the engine.
Two open parts for accommodating a fuel pump must be formed in the top in order to provide two fuel pumps inside the fuel tank. After the fuel pumps are accommodated in the two open parts, each open part is closed by a cover. The covers have passage holes formed therein for extending the supply pipes from the fuel pumps to the outside of the fuel tank. Specifically, covers are used that are specialized for fuel pumps.
When only one fuel pump is provided in accordance with a fuel-saving engine, another cover must be prepared that does not have a passage hole formed therein.
Furthermore, in the case of a saddle fuel tank provided with a main chamber and an auxiliary chamber, a means must be provided for transferring from the auxiliary chamber that does not have a fuel pump to the main chamber that does have a fuel pump.
It is therefore difficult to change the number of fuel pumps (i.e., the vehicle specifications) in accordance with the requirements of a high-output engine or a fuel-saving engine.